JP-A-3-253568 has disclosed a carousel-type sputtering apparatus for depositing a film on a substrate, such as a glass substrate. The carousel-type sputtering apparatus is a rotary batch-type sputtering apparatus, which is configured so that a substrate holder (rotary drum) formed in a polygonal and cylindrical shape are included in a chamber, and magnetrons with rectangular targets held therein are provided inside the chamber. Film deposition is performed by supplying the magnetrons with power to generate plasma on outer surfaces of the targets while rotating the substrate holder with substrates mounted thereon and introducing reaction gases into the chamber.
JP-A-11-241162 has proposed a sputtering method, which continuously monitors a film thickness during film deposition by use of an optical measuring instrument.
Recently, the WDM filer, which has been used in the WDM technique drawing attention in the field of optical fiber communication, is formed by depositing remarkably many films in layers (e.g., about 100 layered films) with films made of a low refractive index material (e.g., SiO2 films) and films made of a high refractive index material (e.g., Ta2O5 films) alternately layered. In production of such a multilayer optical film, it is important for each of the films to be deposited so as to have a desired film thickness accurately as designed. There has been a demand to develop a technique for depositing the respective films rapidly with high precision.
FIG. 27 is a schematic view of a conventional sputtering apparatus for depositing a multilayer optical film. In the sputtering apparatus, a substrate holder 202 formed in a polygonal and cylindrical shape is housed in a substantially cylindrical chamber 200, and the substrate holder 202 has substrates 204 mounted on respective side surfaces. The chamber includes a magnetron sputtering source for deposition of low refractive index films 206 and a magnetron sputtering source for deposition of high refractive index films 208. The former magnetron sputtering source has a target for deposition of low refractive index films (e.g., a Si target) 210 mounted thereon, and the latter magnetron sputtering source has a target for deposition of high refractive index films (e.g., a Ti target) 212 mounted thereon.
The substrate holder 202 is rotated about a central shaft 214. A low refractive index film is deposited on the respective substrates 204 passing in front of the target 210 by supplying power from a sputtering power supply 216 to the magnetron sputtering source 206 to generate plasma in the vicinity of an outer surface of the target 210, and reacting the generated plasma with a gas supplied from a gas inlet tube, which is not shown. Likewise, a high refractive index film is deposited on the respective substrates 204 by supplying power from a sputtering power supply 218 to the magnetron sputtering source 208 to generate plasma on an outer surface of the target 212, and reacting the generated plasma with a gas supplied from the gas inlet tube. The amount of film deposition and the turn-on time periods for the sputtering power supplys 216, 218 (film deposition rate) are previously checked out. A desired multilayer film is deposited by alternately supplying power to the magnetron sputtering sources 216, 218 while controlling the sputtering time periods.
However, the conventional film deposition apparatuses have been difficult to control film thicknesses with high precision. The conventional film deposition apparatuses have caused a problem that productivity is significantly decreased since the film deposition rate needs to be lowered in order to increase the precision of film thicknesses.
JP-A-49-115085 has proposed a method wherein power is intermittently supplied to a sputtering apparatus in a film deposition process, the film thicknesses are measured in turn-off periods (periods without power being supplied), and the measurement results are fed back to a power supply system, though no carousel type sputtering apparatus is referred to in the publication. This method is disadvantageous in that productivity is low since film deposition processes and measuring processes are alternately performed and since film deposition is interrupted during measurement.
In a case wherein each of the film thicknesses is uniformed by a sputtering apparatus (method) using two cathodes and two power supplies for supplying power to the cathodes as disclosed in JP-A-3-253568, the differences between the two cathodes need to be made small with respect to factors affecting the film deposition rate (such as magnetic fields, applied voltages, the surface states of the targets, and gas pressures). However, it is not easy to make each of the film thicknesses uniform since it is difficult to equalize the conditions of both cathodes.
The present invention is proposed in consideration of the circumstances. It is an object of the present invention to provide a sputtering apparatus and a sputter film deposition method, which are capable of controlling film thicknesses with high precision and have excellent productivity. It is another object of the present invention to provide a sputtering apparatus and a sputter film deposition method, which are capable of achieving uniform film deposition more simply than the conventional techniques, making the size of the apparatus smaller and lowering the cost.